I'm hoping someone's run into this before. I dropped an L98 TPI 350 into my 84 (originally carb'd 305). None of the dash harness has been touched - it's all original from the 84. Now my oil gauge is pegged to the right and my temp gauge is 20* hotter than it should be (a diagnostic tool confirmed this). Sending unit on the temp gauge was tested and shown to be working at the correct voltage. Am I SOL in getting these to work with the new motor?

 

I would use a mechanical oil pressure guage on the motor to verify that the oil pressure guage in the car is wrong.

 

Bad senders like to max the gauge, usually as soon as you turn the IGN on

CTS' changed resistance values over the years. You may just have to live with it being a little low if you cant find a CTS from your 84. With coolant, you really only need to know 4 conditions: cold, barely showing a temp, operating temp, and too hot

It should be obvious when each of these conditions are met

 

Not to nit pick (but being nit picky), the CTS is different from the temp gauge sending unit. The CTS should be what was with the TPI. The temp gauge sending unit from the '84 should fit in the L98 head and give the proper reading.

Ditto the oil pressure sending unit. The '84 unit should work with the L98 engine. Also, be aware that a shorted wire will peg the gauge - make sure you didn't pinch that wire somehow during the engine install.

 

Sorry, Ive gotten too used to the newer LS1 combo sensors. You are correct, they are senders